In an active-matrix organic light-emitting diode (AMOLED) display panel, various effects may result in the deterioration of the uniformity of the panel. Since the brightness of the AMOLED display panel is proportional to the current of the organic light emitting diodes, a level of the current will influence the display uniformity of the AMOLED display panel. If the non-uniformity needs to be controlled within a range of about ±1%, the current of the AMOLED display panel needs to be controlled within the range of ±1%. Since most integrated circuits transmit voltage signals rather than current signals, it is difficult to control the brightness of the pixels to be within the range of ±1% in the AMOLED display panel. Furthermore, the voltage signals have to be transformed into the current signals, and then the results of the transformation are stored in the pixels during a frame period. Actually, since the threshold voltages and mobility of transistors in the AMOLED display panel shift over time, these shortcomings may cause the non-uniformity of the brightness of the display panel.
FIG. 1 is a pixel driver circuit diagram illustrating a prior art AMOLED display panel. A pixel driver circuit 10 of the AMOLED display panel mainly includes a first transistor (TFT1) 102, a second transistor (TFT2) 104, a control capacitor (C) 106, a scan line (Gate n) 108, and a data line (Data n) 110. As shown in FIG. 1, the pixel driver circuit 10 of the typical AMOLED display panel does not include a compensation circuit. When variations of the components in the AMOLED display panel occur, driving voltages and carrier mobility will change together, and the pixel driver circuit 10 of the AMOLED display panel cannot compensate the change of the carrier mobility.
Therefore, as mentioned above, there is a significant need to design a compensation circuit of the pixel driver circuit of the AMOLED display panel such that the uniformity and stability of the brightness of the light emission from the display panel are controlled within a permissible range.